#ifndef PIL_DateTime_INCLUDED
#define PIL_DateTime_INCLUDED


#include "../Environment.h"
#include "Timestamp.h"
//#include "Timespan.h"
#include "iostream"

namespace pi {

class PIL_API DateTime
    /// This class represents an instant in time, expressed
    /// in years, months, days, hours, minutes, seconds
    /// and milliseconds based on the Gregorian calendar.
    /// The class is mainly useful for conversions between
    /// UTC, Julian day and Gregorian calendar dates.
    ///
    /// The date and time stored in a DateTime is always in UTC
    /// (Coordinated Universal Time) and thus independent of the
    /// timezone in effect on the system.
    ///
    /// Conversion calculations are based on algorithms
    /// collected and described by Peter Baum at
    /// http://vsg.cape.com/~pbaum/date/date0.htm
    ///
    /// Internally, this class stores a date/time in two
    /// forms (UTC and broken down) for performance reasons. Only use
    /// this class for conversions between date/time representations.
    /// Use the Timestamp class for everything else.
    ///
    /// Notes:
    ///   * Zero is a valid year (in accordance with ISO 8601 and astronomical year numbering)
    ///   * Year zero (0) is a leap year
    ///   * Negative years (years preceding 1 BC) are not supported
    ///
    /// For more information, please see:
    ///   * http://en.wikipedia.org/wiki/Gregorian_Calendar
    ///   * http://en.wikipedia.org/wiki/Julian_day
    ///   * http://en.wikipedia.org/wiki/UTC
    ///   * http://en.wikipedia.org/wiki/ISO_8601
{
public:
    typedef Timestamp::TimeDiff TimeDiff;
    typedef Timestamp::TimeDiff Timespan;
    enum Months
        /// Symbolic names for month numbers (1 to 12).
    {
        JANUARY = 1,
        FEBRUARY,
        MARCH,
        APRIL,
        MAY,
        JUNE,
        JULY,
        AUGUST,
        SEPTEMBER,
        OCTOBER,
        NOVEMBER,
        DECEMBER
    };

    enum DaysOfWeek
        /// Symbolic names for week day numbers (0 to 6).
    {
        SUNDAY = 0,
        MONDAY,
        TUESDAY,
        WEDNESDAY,
        THURSDAY,
        FRIDAY,
        SATURDAY
    };

    DateTime();
        /// Creates a DateTime for the current date and time.

    DateTime(const Timestamp& timestamp);
        /// Creates a DateTime for the date and time given in
        /// a Timestamp.

    DateTime(int year, int month, int day, int hour = 0, int minute = 0,
             int second = 0, int millisecond = 0, int microsecond = 0);
        /// Creates a DateTime for the given Gregorian date and time.
        ///   * year is from 0 to 9999.
        ///   * month is from 1 to 12.
        ///   * day is from 1 to 31.
        ///   * hour is from 0 to 23.
        ///   * minute is from 0 to 59.
        ///   * second is from 0 to 59.
        ///   * millisecond is from 0 to 999.
        ///   * microsecond is from 0 to 999.

    DateTime(double julianDay);
        /// Creates a DateTime for the given Julian day.

    DateTime(Timestamp::UtcTimeVal utcTime, Timestamp::TimeDiff diff);
        /// Creates a DateTime from an UtcTimeVal and a TimeDiff.
        ///
        /// Mainly used internally by DateTime and friends.

    DateTime(const DateTime& dateTime);
        /// Copy constructor. Creates the DateTime from another one.

    ~DateTime();
        /// Destroys the DateTime.

    DateTime& operator = (const DateTime& dateTime);
        /// Assigns another DateTime.

    DateTime& operator = (const Timestamp& timestamp);
        /// Assigns a Timestamp.

    DateTime& operator = (double julianDay);
        /// Assigns a Julian day.

    DateTime& assign(int year, int month, int day, int hour = 0, int minute = 0, int second = 0, int millisecond = 0, int microseconds = 0);
        /// Assigns a Gregorian date and time.
        ///   * year is from 0 to 9999.
        ///   * month is from 1 to 12.
        ///   * day is from 1 to 31.
        ///   * hour is from 0 to 23.
        ///   * minute is from 0 to 59.
        ///   * second is from 0 to 59.
        ///   * millisecond is from 0 to 999.
        ///   * microsecond is from 0 to 999.

    void swap(DateTime& dateTime);
        /// Swaps the DateTime with another one.

    int year() const;
        /// Returns the year.

    int month() const;
        /// Returns the month (1 to 12).

    int week(int firstDayOfWeek = MONDAY) const;
        /// Returns the week number within the year.
        /// FirstDayOfWeek should be either SUNDAY (0) or MONDAY (1).
        /// The returned week number will be from 0 to 53. Week number 1 is the week
        /// containing January 4. This is in accordance to ISO 8601.
        ///
        /// The following example assumes that firstDayOfWeek is MONDAY. For 2005, which started
        /// on a Saturday, week 1 will be the week starting on Monday, January 3.
        /// January 1 and 2 will fall within week 0 (or the last week of the previous year).
        ///
        /// For 2007, which starts on a Monday, week 1 will be the week startung on Monday, January 1.
        /// There will be no week 0 in 2007.

    int day() const;
        /// Returns the day witin the month (1 to 31).

    int dayOfWeek() const;
        /// Returns the weekday (0 to 6, where
        /// 0 = Sunday, 1 = Monday, ..., 6 = Saturday).

    int dayOfYear() const;
        /// Returns the number of the day in the year.
        /// January 1 is 1, February 1 is 32, etc.

    int hour() const;
        /// Returns the hour (0 to 23).

    int hourAMPM() const;
        /// Returns the hour (0 to 12).

    bool isAM() const;
        /// Returns true if hour < 12;

    bool isPM() const;
        /// Returns true if hour >= 12.

    int minute() const;
        /// Returns the minute (0 to 59).

    int second() const;
        /// Returns the second (0 to 59).

    int millisecond() const;
        /// Returns the millisecond (0 to 999)

    int microsecond() const;
        /// Returns the microsecond (0 to 999)

    double julianDay() const;
        /// Returns the julian day for the date and time.

    Timestamp timestamp() const;
        /// Returns the date and time expressed as a Timestamp.

    Timestamp::UtcTimeVal utcTime() const;
        /// Returns the date and time expressed in UTC-based
        /// time. UTC base time is midnight, October 15, 1582.
        /// Resolution is 100 nanoseconds.

    bool operator == (const DateTime& dateTime) const;
    bool operator != (const DateTime& dateTime) const;
    bool operator <  (const DateTime& dateTime) const;
    bool operator <= (const DateTime& dateTime) const;
    bool operator >  (const DateTime& dateTime) const;
    bool operator >= (const DateTime& dateTime) const;

    DateTime  operator +  (const Timespan& span) const;
    DateTime  operator -  (const Timespan& span) const;
    Timespan  operator -  (const DateTime& dateTime) const;
    DateTime& operator += (const Timespan& span);
    DateTime& operator -= (const Timespan& span);

    void makeUTC(int tzd);
        /// Converts a local time into UTC, by applying the given time zone differential.

    void makeLocal(int tzd);
        /// Converts a UTC time into a local time, by applying the given time zone differential.

    static bool isLeapYear(int year);
        /// Returns true if the given year is a leap year;
        /// false otherwise.

    static int daysOfMonth(int year, int month);
        /// Returns the number of days in the given month
        /// and year. Month is from 1 to 12.

    static bool isValid(int year, int month, int day, int hour = 0, int minute = 0, int second = 0, int millisecond = 0, int microsecond = 0);
        /// Checks if the given date and time is valid
        /// (all arguments are within a proper range).
        ///
        /// Returns true if all arguments are valid, false otherwise.

protected:
    static double toJulianDay(Timestamp::UtcTimeVal utcTime);
        /// Computes the Julian day for an UTC time.

    static double toJulianDay(int year, int month, int day, int hour = 0, int minute = 0, int second = 0, int millisecond = 0, int microsecond = 0);
        /// Computes the Julian day for a gregorian calendar date and time.
        /// See <http://vsg.cape.com/~pbaum/date/jdimp.htm>, section 2.3.1 for the algorithm.

    static Timestamp::UtcTimeVal toUtcTime(double julianDay);
        /// Computes the UTC time for a Julian day.

    void computeGregorian(double julianDay);
        /// Computes the Gregorian date for the given Julian day.
        /// See <http://vsg.cape.com/~pbaum/date/injdimp.htm>, section 3.3.1 for the algorithm.

    void computeDaytime();
        /// Extracts the daytime (hours, minutes, seconds, etc.) from the stored utcTime.

private:
    void checkLimit(short& lower, short& higher, short limit);
    void normalize();
        ///utility functions used to correct the overflow in computeGregorian

    Timestamp::UtcTimeVal _utcTime;
    short  _year;
    short  _month;
    short  _day;
    short  _hour;
    short  _minute;
    short  _second;
    short  _millisecond;
    short  _microsecond;

    static const TimeDiff MILLISECONDS; /// The number of microseconds in a millisecond.
    static const TimeDiff SECONDS;      /// The number of microseconds in a second.
    static const TimeDiff MINUTES;      /// The number of microseconds in a minute.
    static const TimeDiff HOURS;        /// The number of microseconds in a hour.
    static const TimeDiff DAYS;         /// The number of microseconds in a day.
};


//
// inlines
//
inline Timestamp DateTime::timestamp() const
{
    return Timestamp::fromUtcTime(_utcTime);
}


inline Timestamp::UtcTimeVal DateTime::utcTime() const
{
    return _utcTime;
}


inline int DateTime::year() const
{
    return _year;
}


inline int DateTime::month() const
{
    return _month;
}


inline int DateTime::day() const
{
    return _day;
}


inline int DateTime::hour() const
{
    return _hour;
}


inline int DateTime::hourAMPM() const
{
    if (_hour < 1)
        return 12;
    else if (_hour > 12)
        return _hour - 12;
    else
        return _hour;
}


inline bool DateTime::isAM() const
{
    return _hour < 12;
}


inline bool DateTime::isPM() const
{
    return _hour >= 12;
}


inline int DateTime::minute() const
{
    return _minute;
}


inline int DateTime::second() const
{
    return _second;
}


inline int DateTime::millisecond() const
{
    return _millisecond;
}


inline int DateTime::microsecond() const
{
    return _microsecond;
}


inline bool DateTime::operator == (const DateTime& dateTime) const
{
    return _utcTime == dateTime._utcTime;
}


inline bool DateTime::operator != (const DateTime& dateTime) const
{
    return _utcTime != dateTime._utcTime;
}


inline bool DateTime::operator <  (const DateTime& dateTime) const
{
    return _utcTime < dateTime._utcTime;
}


inline bool DateTime::operator <= (const DateTime& dateTime) const
{
    return _utcTime <= dateTime._utcTime;
}


inline bool DateTime::operator >  (const DateTime& dateTime) const
{
    return _utcTime > dateTime._utcTime;
}


inline bool DateTime::operator >= (const DateTime& dateTime) const
{
    return _utcTime >= dateTime._utcTime;
}


inline bool DateTime::isLeapYear(int year)
{
    return (year % 4) == 0 && ((year % 100) != 0 || (year % 400) == 0);
}


inline void swap(DateTime& d1, DateTime& d2)
{
    d1.swap(d2);
}

inline std::ostream& operator << (std::ostream &os, const DateTime &dt)
{
    char date[100];
    std::sprintf(date,"%04d-%02d-%02d %02d:%02d:%02d.%03d UTC",
                 dt.year(), dt.month(), dt.day(),
                 dt.hour(), dt.minute(), dt.second(),
                 dt.millisecond());
    return os << date;
}

} // pi


#endif // PIL_DateTime_INCLUDED
